Piezoelectricity and Biocompatibility of Flexible ScAl_(1-N Thin Films for Compliant MEMS Transducers

There is huge research activity in the development of flexible and biocompatible piezoelectric materials for next-generation compliant micro electro-mechanical systems (MEMS) transducers to be exploited in wearable devices and implants. This work reports for the first time on the development of flexible ScAl_(1-N films deposited by sputtering technique onto polyimide substrates, assessing their piezoelectricity and biocompatibility. Flexible ScAl_(1-N films have been analyzed in terms of morphological, structural, and piezoelectric properties. ScAl_(1-N layer exhibits a good surface roughness of 4.40 nm and moderate piezoelectricity with an extracted effective piezoelectric coefficient (d₃₃^eff) value of 1.87 ± 0.06 pm/V, in good agreement with the diffraction pattern analysis results. Cell viability assay, performed to study the interaction of the ScAl_(1-N films with human cell lines, shows that this material does not have significant effects on tested cells. Furthermore, the ScAl_(1-N layer, integrated onto a flexible device and analyzed by bending/unbending measurements, shows a peak-to-peak open-circuit voltage (V_OC) of 0.32 V and a short-circuit current (I_SC) of 0.27 μA, with a generated power of 19.28 nW under optimal resistive load, thus demonstrating the potential of flexible ScAl_(1-N films as active layers for next-generation wearable/implantable piezoelectrics.